Stimulation of the immune system, which includes stimulation of either or both innate immunity and adaptive immunity, is a complex phenomenon that can result in either protective or adverse physiologic outcomes for the host. In recent years there has been increased interest in the mechanisms underlying innate immunity, which is believed to initiate and support adaptive immunity. This interest has been fueled in part by the recent discovery of a family of highly conserved pattern recognition receptor proteins known as Toll-like receptors (TLRs) believed to be involved in innate immunity as receptors for pathogen-associated molecular patterns (PAMPs). Compositions and methods useful for modulating innate immunity are therefore of great interest, as they may affect therapeutic approaches to conditions involving autoimmunity, inflammation, allergy, asthma, graft rejection, graft versus host disease (GvHD), infection, cancer, and immunodeficiency.
Recently there have been a number of reports describing the immunostimulatory effect of certain types of nucleic acid molecules, including CpG nucleic acids and double-stranded RNA. Of note, it was recently reported that Toll-like receptor 9 (TLR9) recognizes bacterial DNA and CpG DNA. Hemmi H et al. (2000) Nature 408:740-5; Bauer S et al. (2001) Proc Natl Acad Sci U S A 98:9237-42. It was also recently reported that immune complexes containing IgG and nucleic acid can stimulate TLR9 and participate in B-cell activation in certain autoimmune diseases. Leadbetter E A et al. (2002) Nature 416:595-8.
Chlroroquines have been recognized as useful not only as anti-malarial agents but also as anti-inflammatory agents. Although its mechanism of action is not well understood, chloroquine has been used effectively in the treatment of various autoimmune diseases, including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). For a review, see Wallace D J (1996) Lupus 5 Suppl 1:S59-64. Recently Macfarlane and colleagues described a number of small molecule analogs and derivatives of chloroquine (4-aminoquinoline) and quinacrine (9-aminoacridine) which reportedly inhibit stimulation of the immune system. U.S. Pat. No. 6,221,882; U.S. Pat. No. 6,479,504; U.S. Pat. No. 6,521,637; PCT published application PCT/US00/16723 (WO 00/76982); and PCT published application PCT/US98/13820 (WO 99/01154). Macfarlane and colleagues report these small molecule inhibitors of the immune response, even when used at nanomolar concentrations, can block the action of immunostimulatory DNA. U.S. Pat. No. 6,221,882 B1. Macfarlane and coworkers studied a large number of compounds by varying substituents on a limited number of 4-aminoquinoline and 9-aminoacridine core structures related to chloroquine and quinacrine.